Over time, an individual may accumulate thousands of digital images in a personal computer. However, the larger the collection of images becomes, the more difficult it can be to find a desired digital image within the collection. One approach to managing a large collection of images is to organize the images into folders named with relevant keywords. An individual may also give the images filenames that include relevant keywords. The keywords associated with an image may be referred to as user tags. The process of associating user tags with images may be a very time consuming, manual process. Consequently, many personal collections of digital images have relatively few, if any, user tags.
In addition, metadata may be used to organize or search collections of digital images. Metadata information is stored as part of the digital image, together with the pixel data. That is, the pixel data encodes the visual attributes of the images, such as hue and brightness, while the metadata encodes supplemental data, such the date and time the image was captured, the camera settings used to capture the image, etc.
Search techniques that use user tags and/or metadata may be referred to in general as tag based. Given the nature of many personal collections or databases of digital images, tag-based search techniques are often ineffective.
Another approach for retrieving or locating a desired image in a large collection of digital images is to use a content-based search technique.